There are many techniques for producing roast and ground coffee extracts which can be concentrated, decaffeinated and/or dried to produce soluble or instant coffee. In order to make the process economically feasible, the yield of coffee solubles from the roast and ground coffee must be high. In order to match the aroma and flavor volatiles which are present in roast and ground coffee, a number of techniques have been used for stripping these volatiles from the roast and ground coffee before and after extraction.
Many of these processes involve steam distillation of the volatile aromatics from the roast and ground coffee. These distillates are condensed and added back to the coffee at some point. It is well known to those skilled in the art that the extract obtained via extraction of steamed coffee is undesirably acidic. Steaming roasted and ground coffee is thought to result in the production of undesirable acids which degrade the quality of coffee extract obtained when extracting the steamed roasted and ground coffees.
Many techniques have been devised for minimizing the production of acids or in some way masking the flavor or aroma of these acids. When the extract produced is to be decaffeinated in a liquid/liquid decaffeination process, this problem becomes even more acute. This is readily apparent since the organic solvents which extract the caffeine from the coffee extract also extract some of the important coffee solubles making the presence of undesirable acids even more apparent to the consumer.
See, for example, U.S. Pat. No. 3,644,123, issued to Pitchon in 1972, in which he notes that by steaming the roast and ground coffee to remove the volatiles and then extracting the coffee, an extract is formed which is undesirably acidic. The pH is about 4.7 due to the increase of "undesirable acids" formed during the steaming operation. Pitchon has found that the pH of the extract can be increased by flowing the extract from the steamed coffee through a bed of unsteamed coffee.
Similarly, U.S. Pat. No. 3,148,070, issued to Mishkin et al. in 1964, also discloses that in order to improve the extract obtained from coffee which has been steam-distilled to strip the aromatic volatiles that the stripped coffee be extracted together with non-steamed coffee in a well known manner. British Pat. No. 1,057,840, published in 1967, also discusses steaming of roast and ground coffee to form a distillate. The steamed coffee is then extracted together with an equal quantity of unsteamed coffee. A portion of this extract is optionally concentrated and freeze-dried in combination with the steam distillate. The remaining portion of the extract is spray-dried and combined with freeze-dried material.
These references and other references in the art teach the desirability of steaming roast and ground coffee to remove flavor and aroma volatiles for later addback to coffee extract. They also teach that this steaming develops undesirable acids which must be subsequently removed or neutralized by co-extraction of an unsteamed coffee.
Surprisingly, it has been found that decaffeination of green beans followed by roasting and conventional extraction produces certain acids in the soluble coffee made therefrom which lend a desirable taste to the final brew. The special steaming process described herein produces these acids within the roast and ground coffee along with undesirable volatile materials. It is an object therefore of this invention to produce a coffee extract having a pH of about 4.7 which contains desirable acids.
It is also an object of the present invention to make a unique coffee extract in which an extract produced from steamed coffee is mixed with an extract produced from unsteamed coffee. When these extracts are decaffeinated in a liquid/liquid process and then concentrated, the undesirable volatiles from the steamed portion are removed. The desirable acids produced during the steaming process contribute a flavor strength to the concentrate.
These and other objects will become apparent from the specification herein.